1. Field of the Invention
The present invention generally relates to components for printheads for inkjet printers and a process for preparation thereof.
2. State of the Art
FIG. 1 shows an example of a conventional printhead for an inkjet printer. The printhead includes a substrate 1, an intermediate layer 2, and an orifice plate 3. As further shown in the drawing, a nozzle 4 is formed in orifice plate 3 and a vaporization cavity 5 is defined between the substrate 1 and the orifice plate 3. For convenience of illustration, the drawing shows only one of the nozzles 4 in the orifice plate; however, a complete inkjet printhead includes an array of circular nozzles, each of which is paired with a vaporization cavity. Moreover, a complete inkjet printhead includes manifolds that connect vaporization cavities to an ink supply.
Furthermore, in a complete printhead, each vaporization cavity includes a heater resistor such as the resistor 6 in FIG. 1. In practice, all of the heater resistors on a printhead are connected in an electrical network for selective activation. When a particular heater resistor receives a pulse, the electrical energy is rapidly converted to heat which then causes ink adjacent to the heater resistor to form a vapor bubble. As the vapor bubble expands due to the heat provided by an energized heater resistor, the bubble ejects a droplet of ink from the nozzle in the orifice plate. This action is schematically illustrated in FIG. 1 with the direction of bubble growth being indicated by the arrow. By appropriate selection of the sequence of energizing the heater resistors, the ejected ink droplets can form patterns such as alphanumeric characters.
To provide an efficient operation of the resistor, a thermal barrier is provided between the resistor and the substrate on which the resistor is located. In the case of flexible substrates, it has been proposed to use a sputtered oxide layer extending completely over the flexible substrate as the thermal barrier. The resistors and conductors overlie the thermal barrier but when the flexible substrate is bent, it has been discovered that cracking of the oxide layer can lead to electrical shorts through the resistors to a metal adhesion layer provided between the resistors and the underlying polymer material.